This applicant claims Paris Convention priority of DE 198 51 173.6 filed Nov. 6, 1998 the complete disclosure of which is hereby incorporated by reference.
The invention concerns a method for producing connection ends on metal hoses which are separated off endless hoses, wherein overlapping metal layers are fixed by means of laser welding prior to separation, as well as a device for the manufacture of connection ends on metal hose pieces which are separated off endless hose, wherein overlapping metal layers are fixed by means of welding prior to separation.
The above mentioned types of metal hose are manufactured by helically winding one or a plurality of layers of metal band. The positive interlocking connection between neighboring band regions and/or layers is effected by V-shaped profiling or folding. The assembly and production lines for hoses of this type produce endless hose or hose sections having a length of several meters.
For subsequent applications, it is necessary to cut the strip wound hose to a certain length appropriate for the application at hand. This separation procedure cannot be carried out through simple perpendicular cutting, since the anchoring between neighboring layers would be partially removed thereby and the ends of the band would spring apart due to the intrinsic tension therein to produce sharp points or wedge-shaped inclusions on the ends of the bands. Hoses having such sprung ends cannot be processed further. For this reason, the ends are fixed prior to separation of the hose piece from the endless hose. This can be effected by means of stamping, pressing or the like, requiring complicated and expensive tools which, in addition, have to be adapted to the hose geometry at hand.
For this reason, one has already proposed the introduction of a large number of welding locations in the form of a stitch seam effected by beam welding to fix the winding layers in the vicinity of the hose ends which are to be produced and to separate using laser welding (DE 44 11 246 A1). Disadvantageously, this procedure leads, in particular, to extensive spatter formation during spot welding of heavily oiled or coated metal bands leading to soiling of the processing optics and gas leads. Also disadvantageous is that either two stitch seams must be produced next to each other or one stitch seam having large spot diameter This latter procedure substantially reduces the processing speed. In addition, the finite separation between welding points can lead to the formation of small tips or pimples following separation
Departing therefrom, it is the underlying purpose of the invention to introduce a method for the production of connection ends of strip wound hose which is flexible as well as economical and to introduce an associated device for carrying out such a method.
This purpose is achieved in accordance with the invention using a method of the above mentioned kind, wherein a laser beam is guided continuously over the entire periphery of the hose piece for production of the welding seam, the laser beam modulated with a cyclic motion through a finite angle with respect to the peripheral direction of the hose piece. The purpose underlying the invention is also solved by a device categorizing the invention having a periodically functioning deflection device for deflecting the laser beam through a finite angle with respect to the peripheral direction of the metal hose.
In principle, the above mentioned sweeping motion can subtend a finite angle with respect to the axis of the hose piece, in particular, in a range between minus 60xc2x0 to plus 60xc2x0 relative to the hose axis. This provides an additional degree of freedom for configuring the geometry of the tacking seam. However, a preferred embodiment provides that the sweeping motion be exercised parallel to the axis of the hose piece. This permits, in particular, sinusoidal or triangular-shaped (zigzag) seams which are normally and preferentially effected as a single seam. It is thereby no longer necessary to create a double seam. Although the sinusoidal or triangular shape of the individual seam leads to a seam length in excess of that of a peripheral seam lying in a plane perpendicular to the axis and therefore Lo longer associated production times, these production times are nevertheless significantly less than the time required to produce two parallel seams with the same specific power introduced into the welding region or to produce a seam having larger spot diameter.
Moreover, the method in accordance with the invention has the substantial advantage that an interlocking material connection is effected directly up to the cutting plane, normally lying in the points of inflection of the welding seam. Typical amplitudes are in the range between 0.5-2 mm and preferentially between 0.5-0.7 mm. Control of the laser power and/or of the laser power density within the welding path can change the path energy to minimize the heat deposition for adaptation to the respective tubing geometries and/or to change the depth of the weld.
The separation of a hose end of an endless hose having a welding seam provided in the above mentioned manner can be preferentially effected using laser beam cutting, wherein a preferred embodiment provides that the separation of the hose ends from endless hose is effected directly following welding in the same processing step. In another preferred embodiment, the separation of the hose pieces is first effected after complete production of the welding seam about the entire periphery of the endless hose, wherein the separation is then preferably carried out with the same laser which produced the welding seam.
Additional preferred embodiments of the method provide that the cyclic motion of the laser beam in the axial direction of the hose piece for producing the peripheral laser welding seam is effected with a substantially higher frequency than the frequency of revolution of the endless hose and, in particular, that the cyclic motion has a frequency on the order of 150-250 Hz.
The deflection device for the laser beam preferentially comprises a deflection mirror which is adapted for steering.
Additional advantages and features of the invention can be derived from the claims and the following description in which embodiments of the method in accordance with the invention are shown and discussed in greater detail with reference to the drawing.